Resistivity is an intrinsic property of a material and a measurement of a material's resistance to the movement of charge through the material. High or low resistivity materials can be used for different applications. For example, low resistivity metal layers in integrated circuits minimize power losses. High resistivity metal layers may be used as heater elements for phase change memory or other applications.
In one example, tungsten layers may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on the silicon substrate. Tungsten nitride layers may be used as diffusion barriers for tungsten interconnects, vias and plugs, providing relatively low resistivity and good adhesion to dielectric layers. Problems regarding the use of low resistivity tungsten layers with tungsten nitride layers, however, have prevented these materials from being used together in semiconductor devices.